Exam 12: Characterizing Stars

What proportion of visible stars in Earth's nighttime sky are members of multiple-star systems, such as binary stars?

Barnard's star, one of Earth's near neighbors, is classified as M5 V. This means that it is a

Which of these CANNOT be determined by examining a star's spectrum?

An astronomer looks through a telescope and identifies a source that appears visually to be a single star. However, the source is later determined to be a binary system looking at its spectrum. Which of these spectral features would NOT characterize it as a binary?

Using the Hertzsprung-Russell diagram (Figure 12-7 in the text), determine which type of star has these characteristics: surface temperature of 40,000 K and luminosity 100,000 times that of the Sun.

The spectrum of a very distant source shows spectral absorption lines of ionized helium, He II, and molecular absorption bands from titanium oxide, TiO. What could one conclude about this star?

Two stars, one classified A4 V and the other A4 III, have the same apparent magnitude. There is no significant amount of absorption of starlight by interstellar material. From this information one knows that the A4 V star is _____ than the A4 III star.

If the Sun were orbited by a star of 1.8 solar masses at Jupiter's distance of 5.2 au (or, more precisely, the Sun and the other star were orbiting each other 5.2 au apart), what would be the orbital period of the system? (It might be useful to compare the answer with the actual orbital period of Jupiter, 11.9 years.)

How are white dwarfs treated in the luminosity class definitions?

A particular star appears brighter seen through a blue filter than seen through a yellow filter. Which of these surface temperatures is possible for this star?

If star A has an apparent magnitude of +5 and star B has an apparent magnitude of +10, then

The star Regulus, in the constellation Leo, appears brighter through a blue filter than it does through a yellow filter. Suppose that a second star is found that has the same brightness as Regulus through the blue filter but is brighter than Regulus through the yellow filter. From this information, one can say conclusively that the second star has

Sirius, in Canis Major (the large hunting dog of Orion), is the brightest star in the northern hemisphere winter night sky. It has a parallax angle of 0.38 arcseconds. The brightest star in Orion's other hunting dog, Canis Minor, is Procyon, with a parallax angle of 0.29 arcseconds. Vega, in Lyra (the Lyre [Harp]), is the brightest star in the northern summer night sky. It has a parallax angle of 0.13 seconds of arc. Which of these stars is farthest away?

Which one of these properties is NOT needed to determine individual masses in a binary star system?

Two stars, P and Q, can be seen in the same region of Earth's sky with the same apparent magnitude, but star Q is twice as far away as star P. What is the ratio of the luminosities of these stars (star P/star Q)?

A red supergiant star is found to have a surface temperature of 2500 K and a luminosity 100,000 times that of the Sun. Use the Hertzsprung-Russell diagram in Figure 12-8 in the text to determine its approximate radius compared with that of the Sun.

The star Alderamin has an apparent magnitude of 2.4 and an absolute magnitude of 1.4. The star Merak has an apparent magnitude of 2.4 and absolute magnitude of 0.5. Assuming that neither star has been dimmed by interstellar clouds, one can say for sure that Merak is

The spectrum of a star shows these absorption line characteristics: very strong H, weaker Mg II and Si II, and no He I or Ca II lines. What is the spectral type of this star?

As one moves along the main sequence, the masses of stars

Spica (in Virgo) and Hador (in Centaurus) have about the same temperature. However, Hador has roughly 4 times the luminosity of Spica. What can one determine about the relative radii of these two stars? Spica is about